Radioactive Seed Localization

Margarita Zuley, MDAssociate Professor of Radiology

University of PittsburghMedical Director Breast ImagingMagee Womens Hosp of UPMC

Thank you to Mike Sheetz Thank you to Mike Sheetz

University of Pittsburgh RSO University of Pittsburgh RSO

Background

Significantly decayed I-125 seeds Significantly decayed I-125 seeds used for brachytherapy used for brachytherapy

Assayed activity approx 200 Assayed activity approx 200 microcuriesmicrocuries

Half-life of I-125 is 60 daysHalf-life of I-125 is 60 days Can be placed into the breast like a Can be placed into the breast like a

biopsy clip easily with ultrasound or biopsy clip easily with ultrasound or mammography guidancemammography guidance

Background

Work pioneered by Mayo ClinicWork pioneered by Mayo Clinic Almost no contraindications to Almost no contraindications to

placementplacement Used to localize lesion in breast for

surgical excision Emit a different frequency energy Emit a different frequency energy

than Tc-99m and so can be detected than Tc-99m and so can be detected in the OR even with a sentinel node in the OR even with a sentinel node injection of Tc-99minjection of Tc-99m

Benefits

Studies indicate reduced incidence of positive margins compared to wire localization

Allows for improved surgical approach and removal of lesion

Reduces scheduling conflicts between surgeon’s and radiologist’s offices

Regulatory Oversight PA Department of Environmental Protection PA Department of Environmental Protection

Bureau of Radiation Protection regulates Bureau of Radiation Protection regulates use of radioactive material (RAM) in use of radioactive material (RAM) in medicinemedicine

Apply to DEP for a RAM license if not pre-Apply to DEP for a RAM license if not pre-existingexisting

RSL is an off-label use of a deviceRSL is an off-label use of a device

Radiation Safety Office or Officer must be Radiation Safety Office or Officer must be involved from the very beginninginvolved from the very beginning

Coordinated Program

Radiation Safety Office Radiation Safety Office Oversees protocol of training/ Oversees protocol of training/

implementationimplementation Develops policies for handlingDevelops policies for handling Develops policies for storage and Develops policies for storage and

transfertransfer Develops policies for lost/ Develops policies for lost/

damaged seedsdamaged seeds

Training Requirements

Didactic training provided by RSO Didactic training provided by RSO on RSL policies and procedureson RSL policies and procedures

Supervised work experienceSupervised work experience Radiologist – minimum of 2 casesRadiologist – minimum of 2 cases Surgeon – minimum of 1 caseSurgeon – minimum of 1 case Pathologist or PA – minimum of 1 casePathologist or PA – minimum of 1 case

Specific medical staff privilege for Specific medical staff privilege for radiologists and surgeonsradiologists and surgeons

Annual refresher training Annual refresher training

Radiation Safety Issues

Personnel ExposurePersonnel Exposure InventoryInventory Source LeakageSource Leakage SurveysSurveys SecuritySecurity

Radiation Exposure to the Population of the United States

NCRP Report No. 160

Early 1980’s 2006Effective Dose per Individual 360 620In the U.S. Population (mrem)

Early 1980’s 2006Effective Dose per Individual 360 620In the U.S. Population (mrem)

1980’s 2006Effective Dose per Individual 360 620in the U.S. Population (mrem)

Radiation Exposure Potential

Distance (cm) mrem/min

11 2020

1010 0.20.2

100100 0.0020.002

Dose Rate from 200 uCi I-125 seed

Medical Imaging Doses

Procedure Effective Dose (mrem)

Chest x-rayChest x-ray 22

MammogramMammogram 4040

Abdomen x-rayAbdomen x-ray 150150

NM Bone ScanNM Bone Scan 400400

Abdomen CTAbdomen CT 600600

Coronary CTACoronary CTA 10001000

Mettler et al. Radiology 2008

Annual Occupational Exposure Limits: Whole body – 5000 mrem Extremity – 50,000 mrem

Radiation Safety

ALARA Philosophy (As Low As ALARA Philosophy (As Low As Reasonably Achievable)Reasonably Achievable)

Radiation Protection MeasuresRadiation Protection Measures Time (plan in advance)Time (plan in advance) Distance (reverse action tweezers)Distance (reverse action tweezers) Shielding (lead containers for transport Shielding (lead containers for transport

and storage)and storage) Radiation dosimetry not requiredRadiation dosimetry not required

Radiation Safety Issues

InventoryInventory - Constant tracking of seed with - Constant tracking of seed with computerized inventory systemcomputerized inventory system

Source Leakage Source Leakage – Radioactivity is sealed – Radioactivity is sealed inside titanium wall which is “soft” and can be inside titanium wall which is “soft” and can be easily cuteasily cut

SurveysSurveys – Radiation monitoring is performed – Radiation monitoring is performed with gamma probe or NaI meter to locate with gamma probe or NaI meter to locate seedseed

SecuritySecurity – Seeds must be kept in secured – Seeds must be kept in secured area or be under supervision of authorized area or be under supervision of authorized individualindividual

Coordinated Program

RadiologistRadiologist SurgeonSurgeon PathologistPathologist AdministratorsAdministrators All clinicians must have initial All clinicians must have initial

training by someone skilled in the training by someone skilled in the procedure.procedure.

Can have a super user in each Can have a super user in each specialty that trains peersspecialty that trains peers

Form a team with the RSO to Form a team with the RSO to implement the programimplement the program

Consider seed movement

Order and receipt in Nuclear MedicineOrder and receipt in Nuclear Medicine Storage in Breast Imaging Storage in Breast Imaging Placed under US or mammo guidancePlaced under US or mammo guidance Surgical removal in ORSurgical removal in OR Specimen radiography in breast imagingSpecimen radiography in breast imaging Seed removed from specimen in Seed removed from specimen in

pathologypathology Used seeds stored in breast imagingUsed seeds stored in breast imaging RSO picks up spent seeds for disposalRSO picks up spent seeds for disposal

I-125 Seed Ordering

Order seeds separately and Order seeds separately and place them into needles in place them into needles in radiology radiology Have to consider sterilityHave to consider sterility Less expensiveLess expensive

Order prepackaged seeds Order prepackaged seeds that are already sterilethat are already sterile

I-125 Seed Implant

Prescription for implant completed and Prescription for implant completed and signed by radiologist prior to implantsigned by radiologist prior to implant

Seed implanted under radiographic or Seed implanted under radiographic or ultrasonic guidance by authorized ultrasonic guidance by authorized radiologistradiologist

Confirmatory mammogram taken to Confirmatory mammogram taken to verify seed placementverify seed placement

Survey of room performed to assure Survey of room performed to assure seed not dropped or cutseed not dropped or cut

I-125 Seed Implant

Seed is positioned at Seed is positioned at the center of the lesionthe center of the lesion

Seed cannot be Seed cannot be repositionedrepositioned

Rare incidence of seed Rare incidence of seed migrationmigration

Surgery to remove Surgery to remove seed must be seed must be scheduled within 1 scheduled within 1 half life (60 days)half life (60 days)

Patient Instruction

Patient provided written information Patient provided written information on radioactive seed localization on radioactive seed localization option from surgeonoption from surgeon

No special instruction given to No special instruction given to patient with respect to radiation patient with respect to radiation exposure to othersexposure to others

Emphasis that patient must return Emphasis that patient must return for scheduled surgery to remove for scheduled surgery to remove radioactive seedradioactive seed

Surgical Removal Of I-125 Seed

Identification of Identification of surgical patient surgical patient containing I-125 containing I-125 seedseed

Handheld gamma Handheld gamma probe is scanned probe is scanned across breastacross breast Probe set at 27 keV Probe set at 27 keV

to detect gamma to detect gamma radiation from I-125radiation from I-125

Gamma Probe Spectrum for I-125 and Tc-99m

Surgical Removal Of I-125 Seed

Point of greatest Point of greatest activity locates activity locates seed and lesionseed and lesion

Surgical incision Surgical incision is made over is made over “hot spot”“hot spot”

Gamma probe is Gamma probe is used to guide used to guide the excision of the excision of the lesionthe lesion

Steps After Resection of Lesion

Survey specimen with gamma probe Survey specimen with gamma probe to confirm presence of radioactive to confirm presence of radioactive seedseed

Survey surgical site to confirm Survey surgical site to confirm absence of radioactive seedabsence of radioactive seed

Place specimen in plastic container, Place specimen in plastic container, label with radiation sticker, label with radiation sticker, transport to Breast Care Center for transport to Breast Care Center for radiographradiograph

Surgical Concerns

Cutting of radioactive seedCutting of radioactive seed No dissection with scissorsNo dissection with scissors

Suctioning of seed from surgical siteSuctioning of seed from surgical site Misidentification of I-125 seed Misidentification of I-125 seed

radiation from Tc-99m sentinel node radiation from Tc-99m sentinel node activityactivity

Pathology

Specimen transported Specimen transported from BCC back to from BCC back to OR/Pathology labOR/Pathology lab

Number of seeds in Number of seeds in specimen noted on specimen noted on container lidcontainer lid

Locate seed(s) in Locate seed(s) in specimen using specimen using radiograph and/or radiograph and/or gamma probegamma probe

Pathology Remove seed using Remove seed using

scalpel (no scissor scalpel (no scissor dissection)dissection)

Place seed into plastic Place seed into plastic vial with patient RX vial with patient RX number using reverse number using reverse action tweezers, action tweezers, secure cap, and put secure cap, and put vial in lead pigvial in lead pig

Pathology

Scan breast tissue specimen with Scan breast tissue specimen with gamma probe before releasing gamma probe before releasing for sectioningfor sectioning

Complete seed removal log sheetComplete seed removal log sheet Breast Care Center techs will Breast Care Center techs will

pick-up container with pick-up container with radioactive seed(s) at end of dayradioactive seed(s) at end of day